Characteristics of recent glacier variations in Patagonia, Southern Andes

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The project aims at investigating the processes and mechanisms of variations of Patagonian glaciers in response to climatic changes. Field researches were carried out from 9 November to 27 December 1990 at Upsala, Moreno and Tyndall glaciers in the Southern Patagonia. Analyses were made in the budget year of 1991, and the following results were obtained.1) Surface heights of glaciers : Surface profiles were obtained by the triangulation method at the ablation areas of the three glaciers. Tyndall Glacier has thinned by about 20 m from 1985 to 1990, that is a considerably large thinning rate.2) Variations in glacier fronts : Based on field observations, aerial photographs and satellite images, it became clear that Upsala Glacier has been in a recessive stage with a rate of about 500 m/year, whereas Moreno Glacier is considered to have been nearly in the equilibrium condition. An aerial photographic survey made around the Northern Icefield revealed that glaciers on the- western side have retreated in greater degree than on the eastern side.3) Ice-flow : At Upsala Glacier, a considerably rapid velocity of about 3.6 m/d was obtained near the medial moraine. Velocities along transverse lines ranged from 0.38 to 2 m/d at Moreno Glacier, and from 0.07 to 0.51 m/d at Tyndall Glacier.4) Ice thickness : Ice thicknesses were successfully obtained using an impulse radar at Tyndall Glacier, the maximum being about 600 m at 3 km from the left margin. Distribution of foliation patterns and medial moraines were also analyzed.5) Meteorological conditions : Some meteorological characteristics and ablation of ice were studied at Tyndall Glacier.6) Geomorphology : By analyzing the glacial deposits and moraine systems, variation of Upsala Glacier since the late Holocene was elucidated. Distributions of moraines and ice-scoured topography were also investigated around Tyndall Glacier.